miRNAs In Breast Cancer Research Articles

Differential regulation of p130Cas by miRNAs in breast cancer

p regulates cell adhesion and migration by mediating tyrosine receptor kinase signaling. Tight regulation of p130Cas expression is critical for the maintenance of cell motility, survival and apoptosis in various cell types. Several studies reveal that transcriptional and post-translational control of p130Cas is important to maintain its expression and activity. To explore novel regulatory mechanisms for p130Cas expression, we investigated the effect of microRNAs on p130Cas level in human breast cancer cells. Here, we provide experimental evidences that miR-329 is a novel factor regulating p130Cas expression. miR-329 down-regulates cell migration and invasion thereby suppress tumor growth via down-regulating p130Cas. Ectopic expression of p130Cas restored the inhibitory effects of miR-329 in tumor progression. Interestingly, relative expression of miR-329 and p130Cas is inversely correlated between normal and breast cancers; miR-329 decreased, while p130Cas increased in breast cancers. Taken together, our results suggest that miR-329 is a novel factor regulating p130Cas expression and aberrant expression of p130Cas is responsible for tumor progression in breast cancers.

Comprehensive expression analysis of miRNA in breast cancer at the miRNA and isomiR levels

Breast cancer (BC) is the main factor that leads cause of cancer death in women worldwide. A class of small non-coding RNAs, microRNAs (miRNAs), has been widely studied in human cancers as crucial regulatory molecule. Recent studies indicate that a series of isomiRs can be yielded from a miRNA locus, and these physiological miRNA isoforms have versatile roles in miRNA biogenesis. Herein, we performed a comprehensive analysis of miRNAs at the miRNA and isomiR levels in BC using next-generation sequencing data from The Cancer Genome Atlas (TCGA). Abnormally expressed miRNA (miR-21, miR-221, miR-155, miR-30e and miR-25) and isomiR profiles could be obtained at the miRNA and isomiR levels, and similar biological roles could be detected. IsomiR expression profiles should be further concerned, and especially isomiRs are actual regulatory molecules in the miRNA–mRNA regulatory networks. The study provides a comprehensive expression analysis at the miRNA and isomiR levels in BC, which indicates biological roles of isomiRs.

Combined microRNA and ER expression: a new classifier for familial and sporadic breast cancer patients.

BackgroundThe role of miRNAs in familial breast cancer (fBC) is poorly investigated as also in the BRCA-like tumors. To identify a specific miRNA expression pattern which could allow a better fBC classification not only based on clinico-pathological and immunophenotypical parameters we analyzed miRNA profile in familial and sporadic samples. Moreover since BRCA1 tumors and sporadic triple negative (TN) breast tumors share similarities regarding clinical outcomes and some histological characteristics, we focused on TN and not TN cases.MethodsThe sample set included fresh frozen tissue samples, including 39 female fBCs (19 BRCA-related and 20 BRCAX) and 12 male fBC (BRCAX). Moreover, we considered TN and non TN (NTN), 21 BRCA-related and 27 sporadic BCs. MiRNA profiling was performed through GeneChip miRNA v.1.0 Array (Affymetrix). ANOVA, hierarchical and consensus clustering analyses allowed identification of pattern of expression of miRNAs and pathway enrichment analysis, considering validated target genes, was carried out to achieve a deeper biological understanding.ResultsANOVA test led to the identification of 53 deregulated miRNAs; hierarchical and consensus clustering of female fBCs (fFBCs) and male fBCs (fMBCs) highlighted the presence of 3 sample clusters named FBC1, FBC2 and FBC3. We found a correlation between ER-status and the three sample clusters. The three clusters are distinct by a different expression of two clusters of miRNAs (CLU1 and CLU2), which resulted to be different in targeted pathways. In particular, CLU1 targets cellular pathways and CLU2 is involved in epigenetic activities. Considering TN and NTN BRCA-related and sporadic tumors, a hierarchical clustering identified two clusters of miRNAs, which were not so different from CLU1 and CLU2, both in miRNA content and targeted pathways.ConclusionsOur results highlighted the importance of miRNA regulation to better clarify similarities and differences between familial and sporadic BC groups.

Abstract PR5: Prognostic value of miRNAs in breast cancer: Molecular type and patient race

Abstract Background: MicroRNAs (miRNAs) are a class of conserved, non-coding RNAs that are dysregulated in various cancers, including breast cancers. The potential of miRNAs to serve as biomarkers for breast cancer diagnosis and prognosis is being explored, but their clinical value based on race/ethnicity and molecular subtypes (luminal and triple negative breast cancers, TNBCs) has not been examined. Thus, we evaluated expression levels of a panel of miRNAs in luminal (A and B) breast cancers and TNBCs of African Americans (Blacks) and non-Hispanic Caucasians (Whites). We further evaluated the prognostic value of miRNAs based on molecular type of breast cancer and patient race. Methods: TaqMan® miRNA assays were used to quantify expression of miR-181a, miR181b, miR-21, miR-106a, miR-155, miR-210, miR-335, miR-206, and miR-126 in 105 breast cancers (luminal=51 and TNBCs=54) and their corresponding benign/normal tissues. Cancer tissuefrom 48 Blacks (luminal=23 and TNBCs=25) and 57 Whites (luminal=28 and TNBC=29) were analyzed. Fold change in the expression levels between tumor-normal pairs were determined using the 2-∆∆Ct method. A cutoff value for each miRNA was determined by utilizing the Cutoff Finder software application [PLoS ONE 7(12):e51862, 2012]. The cutoff values were used to categorize the tumors into two groups (High expression or positive and low expression or negative). The expression status of tumors was correlated with patient overall survival by univariate Kaplan-Meier analysis. Results: Since the survival probabilities of Blacks and Whites with TNBCs (log rank, p=0.899) were similar, TNBCs from both racial groups were pooled. Similarly, no survival differences were noted in patients of both racial groups with luminal breast cancers (log rank, p=0.178). Therefore, luminal cancers of Blacks and Whites were also pooled together to perform survival analyses based on miRNA expression levels. MiRNA expression profiling studies indicated that, in both the racial groups, miR-181a, miR-181b, miR-21, miR-106a, miR-155, and miR-210 were up-regulated in luminal cancers and TNBCs. In contrast, miR-335, miR-206, and miR-126 were down-regulated in both molecular types. When the prognostic value of miRNAs was evaluated in each molecular type separately, it was found that over-expression of miR-106a (p=0.037) and miR-210 (p=0.039) were associated with poor prognosis of TNBCs. However, none of the evaluated miRNAs were useful in assessing the prognosis of patients with luminal cancers. Conclusions: These findings suggest that increased expression of miR-106a and miR-210 were poor prognostic indicators of TNBCs collected from both Black and White patients. Additionally, our results suggest that in the evaluation of clinical utility of miRNAs molecular types of breast cancer should be considered. This study was funded in part by the National Cancer Institute of the National Institute of Health UAB/TU/MSM Partnership grant (U54 CA118948). This abstract is also presented as Poster C21. Citation Format: Balananda-Dhurjati Kumar Putcha, Trafina Jadhav, Shantel Hebert-Magee, Jeehyun Helen Bae, Andra R. Frost, Isam-Eldin Eltoum, Sejong Bae, Upender Manne. Prognostic value of miRNAs in breast cancer: Molecular type and patient race. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr PR5. doi:10.1158/1538-7755.DISP13-PR5

MicroRNA-335 inhibits proliferation, cell-cycle progression, colony formation, and invasion via targeting PAX6 in breast cancer cells.

microRNAs (miRNAs) have been demonstrated to play crucial roles in tumorigenesis. However, the molecular mechanism underlying the roles of miRNAs in breast cancer remains largely unknown. In this study, we showed that miR-335 is downregulated in a number of breast cancer tissues and cell lines. Luciferase reporter assays identified the paired box 6 gene (PAX6) as a novel target of miR-335. Further investigation revealed that miR-335 negatively regulates the expression of PAX6 in human breast cancer MCF-7 cells. Our results further suggested that overexpression of miR-335 inhibits MCF-7 cell proliferation by inducing cell-cycle arrest at the G1 phase via targeting PAX6. Western blot analysis showed that overexpression of miR-335 promotes p27 protein expression but inhibits cyclin D1 expression in MCF-7 cells; however, overexpression of PAX6 decreased the p27 protein level but increased the cyclin D1 protein level in MCF-7 cells. Furthermore, miR-335 overexpression reduced colony formation and cellular invasion in MCF-7 cells, an effect that was reversed by PAX6 overexpression. In conclusion, this study provides novel insights into the in vitro regulatory patterns of miRNA-335 and PAX6 in breast cancer, and indicates that miRNA-335 may constitute a promising candidate for the treatment of breast cancer.

Diagnostic value of circulating microRNAs as biomarkers for breast cancer: a meta-analysis study

Recent studies have provided new insights into the diagnostic value of circulating microRNAs (miRNAs) for breast cancer (BCa). However, the inconsistent results between studies have prevented the widespread usage of miRNAs in clinics. To systematically assess the potential diagnostic value of circulating miRNAs in BCa, we performed a comprehensive meta-analysis. Eligible studies were retrieved by searching electronic databases. The quality of the studies was assessed on the basis of quality assessment for studies of diagnostic accuracy (QUADAS) criteria. The bivariate meta-analysis model was employed to summarize the diagnostic indices and plot the summary receiver operator characteristic (SROC) curve. A total of 15 studies were included in this meta-analysis, involving 1368 BCa patients and 849 healthy controls. Our bivariate random effects meta-analysis yielded an area under curve (AUC) value of 0.9217, with a sensitivity of 0.82 (95 % confidence interval (CI) 0.80-0.83) and specificity of 0.82 (95% CI 0.80-0.85) for the use of miRNAs in differentiating BCa patients from healthy controls. Notably, our subgroup analysis suggested that a combination of multiple miRNAs (AUC, sensitivity, and specificity of 0.9518, 0.87, and 0.88, respectively) seemed to harbor higher accuracy than single miRNA-based assays (AUC, sensitivity, and specificity of 0.8923, 0.79, and 0.77, respectively). Altogether, our data indicate that circulating miRNA profiling has a potential to be used as a screening test for BCa, among which, the detection of a combined multiple miRNAs may be a more comprehensive indicator than individual miRNA.

Identification of microRNA-93 as a functional dysregulated miRNA in triple-negative breast cancer.

MicroRNAs (miRNAs) are widely recognized as key players in cancer progression and drug resistance, but less is known about the role of miRNAs in triple-negative (estrogen receptor, progesterone receptor, and HER-2/neu) breast cancer (TNBC). The aim of the present study was to examine the expression profile of miRNAs and to explore their possible roles in TNBC. Differentially expressed miRNAs were identified by miRNA microarray and verified by quantitative real-time polymerase chain reaction. The expression of miR-93 was assessed by in situ hybridization in 119 cases of breast cancer. Cell proliferation potential was examined by MTT assay. Cell migration and invasion abilities were evaluated by a wound healing assay and transwell invasion or migration assay. Seven upregulated and ten downregulated miRNAs in TNBC were identified. The miR-93 expression level in TNBC tissues was significantly higher than that in non-triple-negative breast cancer tissues. The potentials of proliferation, invasion, and metastasis in breast cancer MCF-7 cells were promoted by ectopic transfection of miR-93. Our study found several distinct differentially expressed miRNAs in TNBC, as compared to non-triple-negative breast cancer. Among them, miR-93 may be considered as a biomarker associated with the biological and clinical characteristics of human TNBC.

MiR-638 mediated regulation of BRCA1 affects DNA repair and sensitivity to UV and cisplatin in triple-negative breast cancer.

IntroductionTriple-negative breast cancer (TNBC) represents 15 to 20% of all types of breast cancer; however, it accounts for a large number of metastatic cases and deaths, and there is still no effective treatment. The deregulation of microRNAs (miRNAs) in breast cancer has been widely reported. We previously identified that miR-638 was one of the most deregulated miRNAs in breast cancer progression. Bioinformatics analysis revealed that miR-638 directly targets BRCA1. The aim of this study was to investigate the role of miR-638 in breast cancer prognosis and treatment.MethodsFormalin-fixed, paraffin-embedded (FFPE) breast cancer samples were microdissected into normal epithelial and invasive ductal carcinoma (IDC) cells, and total RNA was isolated. Several breast cancer cell lines were used for the functional analysis. miR-638 target genes were identified by TARGETSCAN-VERT 6.2 and miRanda. The expression of miR-638 and its target genes was analyzed by real-time qRT-PCR and Western blotting. Dual-luciferase reporter assay was employed to confirm the specificity of miR-638 target genes. The biological function of miR-638 was analyzed by MTT chemosensitivity, matrigel invasion and host cell reactivation assays.ResultsThe expression of miR-638 was decreased in IDC tissue samples compared to their adjacent normal controls. The decreased miR-638 expression was more prevalent in non-TNBC compared with TNBC cases. miR-638 expression was significantly downregulated in breast cancer cell lines compared to the immortalized MCF-10A epithelial cells. BRCA1 was predicted as one of the direct targets of miR-638, which was subsequently confirmed by dual-luciferase reporter assay. Forced expression of miR-638 resulted in a significantly reduced proliferation rate as well as decreased invasive ability in TNBC cells. Furthermore, miR-638 overexpression increased sensitivity to DNA-damaging agents, ultraviolet (UV) and cisplatin, but not to 5-fluorouracil (5-FU) and epirubicin exposure in TNBC cells. Host cell reactivation assays showed that miR-638 reduced DNA repair capability in post UV/cisplatin-exposed TNBC cells. The reduced proliferation, invasive ability, and DNA repair capabilities are associated with downregulated BRCA1 expression.ConclusionsOur findings suggest that miR-638 plays an important role in TNBC progression via BRCA1 deregulation. Therefore, miR-638 might serve as a potential prognostic biomarker and therapeutic target for breast cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-014-0435-5) contains supplementary material, which is available to authorized users.

Gene regulatory networks by transcription factors and microRNAs in breast cancer.

Gene regulatory networks (GRNs) affect numerous cellular processes and every process of life, and abnormalities of GRN lead to breast cancer. Transcription factors (TFs) and microRNAs (miRNAs) are two of the best-studied gene regulatory mechanisms. However, the architecture and feature of GRNs by TFs and miRNAs in breast cancer and its subtypes were unknown. In this study, we investigated the GRNs by TFs and miRNAs with emphasis on breast cancer classifier genes at system level.

Integrated miRNA and mRNA profiling of tumor-educated macrophages identifies prognostic subgroups in estrogen receptor-positive breast cancer

IntroductionVarious studies have identified aberrantly expressed miRNAs in breast cancer and demonstrated an association between distinct miRNAs and malignant progression as well as metastasis. Even though tumor-associated macrophages (TAM) are known mediators of these processes, little is known regarding their miRNA expression upon education by malignant cells in vivo. MethodsWe profiled miRNA and mRNA expression of in vitro tumor-educated macrophages (TEM) by indirectly co-culturing with estrogen-receptor-positive (ER+) MCF-7 breast cancer cells. The prognostic power of the resulting miRNA list was investigated in primary breast cancer datasets and compared to other signatures. Furthermore, miRNA expression levels were correlated to mRNA expression of macrophage markers and the impact on prognosis was assessed. ResultsThrough the evaluation of the group effects between differentially-expressed miRNAs and their target mRNAs in TEM, the power of detecting regulated miRNAs was greatly increased. The resulting list of 96 miRNAs predicts disease-free survival (DFS) in external datasets of ER+ breast cancer patients and performs well in comparison with other miRNA signatures. Clustering with the predefined miRNA list revealed a significant difference in survival between the two resulting patient groups. Furthermore, an optimized miRNA list, based on correlations with macrophages markers, proved even more capable at identifying patient clusters significantly differing in DFS. ConclusionsIn vitro profiling of TEM and subsequent bioinformatic verification identified miRNAs with a high prognostic power for DFS when transferred into the clinical setting of primary breast cancer. The resulting miRNAs not only verify previously established findings but also lead to new prognostic markers. Furthermore, our data suggest that TAM contribute to the total miRNA expression profile of ER + breast cancers.

The expression and significance of five types of miRNAs in breast cancer.

BackgroundThis study aimed to investigate the expression and significance of 5 types of miRNAs in breast cancer to provide a theoretical and practical foundation for using these miRNAs in the diagnosis and treatment of breast cancer, thereby improving medical services.Material/MethodsStem-loop real-time RT-PCR was used to detect the expression levels of miR-145, miR-21, miR-10b, miR-125a, and miR-206 in 35 cases of breast cancer and adjacent normal breast tissues, and to analyze the relationship of miRNAs expression with clinicopathological features of breast cancer. The expression levels of estrogen receptor (ER) and progesterone receptor (PR) were examined by immunohistochemistry. Fluorescence in situ hybridization was used for the detection of HER-2 and TOP 2A.ResultsThe expression levels of miR-145, miR-125a, and miR-206 in breast cancer were lower than those in adjacent normal tissues. MiR-145 was negatively correlated with tumor size, lymph node metastasis, ER, HER-2, and TOP 2A (P<0.05), regardless of age, menstruation, and PR. MiR-125a was correlated with negative node status, negative HER-2 status (P<0.05), whereas tumor size, age, menstruation, ER, and PR were independent factors. MiR-206 expression was correlated with negative ER status, negative PR status, and negative HER-2 status (P<0.05), regardless of age, menstruation, lymph node metastasis, and TOP 2A. MiR-21 and miR-10b expression in breast cancer tissues was significantly higher than that in adjacent tissues (P<0.05). MiR-21 in post-menstrual patients with lymph node metastasis was highly expressed (P<0.05), and had no correlations with tumor size, ER, PR, and TOP 2A expression. MiR-10b expression was positively correlated with breast cancer tumor size, lymph node metastasis, and TOP 2A status (P<0.05), but had no correlations with age, menstruation, ER, PR, and HER-2.ConclusionsMiR-145, miR-21, miR-10b, miR-125a, and miR-206 may play important roles in breast cancer development and invasion.

The role of microRNA in resistance to breast cancer therapy.

MicroRNAs (miRNAs) are small noncoding RNA molecules with big implications in cancer. The abnormal expression of specific miRNAs has been linked to development of many cancer types. Dysregulated miRNAs play a significant role in proliferation, invasion, differentiation, apoptosis, and resistance of various cancer cells, and considered as oncogenes or tumor-suppressor genes. Findings have shown abnormal expression of specific miRNAs in breast tumors is a strong indication about the resistance to conventional cancer therapy methods. Acquired cancer resistance is a complex, multifactorial occurrence that requires various mechanisms and processes, however, recent studies have suggested that resistance may be linked to treatment-induced dysregulation of miRNAs. This dysregulation of miRNAs can affect the protein expression in cells, the ability for anti-cancer drugs to reach their targets within cells, and the apoptotic pathways. Controlling the expression of these miRNAs alters the resistant phenotype of breast cancer to a nonresistant one. This review focuses on the role of dysregulated miRNAs in breast cancer that are linked to resistance against chemo-, radiation, hormone, and targeted therapies. Finally, the role of miRNAs in breast cancer metastasis is briefly discussed.

Metformin may function as anti-cancer agent via targeting cancer stem cells: the potential biological significance of tumor-associated miRNAs in breast and pancreatic cancers.

Metformin is one of the most used diabetic drugs for the management of type II diabetes mellitus (DM) in the world. Increased numbers of epidemiological and clinical studies have provided convincing evidence supporting the role of metformin in the development and progression of a variety of human tumors including breast and pancreatic cancer. Substantial pre-clinical evidence from in vitro and in vivo experimental studies strongly suggests that metformin has an anti-cancer activity mediated through the regulation of several cell signaling pathways including activation of AMP kinase (AMPK), and other direct and indirect mechanisms; however, the detailed mechanism(s) has not yet been fully understood. The concept of cancer stem cells (CSCs) has gained significant attention in recent years due its identification and defining its clinical implications in many different tumors including breast cancer and pancreatic cancer. In this review, we will discuss the protective role of metformin in the development of breast and pancreatic cancers. We will further discuss the role of metformin as an anti-cancer agent, which is in part mediated through targeting CSCs. Finally, we will discuss the potential role of metformin in the modulation of tumor-associated or CSC-associated microRNAs (miRNAs) as part of the novel mechanism of action of metformin in the development and progression of breast and pancreatic cancers.

Overexpression of miR‐20b inhibits the expression of HIF‐1α and STAT‐3 in invasive ductal carcinoma of the breast (1138.2)

It is known that the hypoxia inducible factor‐1α (HIF‐1α) and the signal transducer and activator of transcription 3 (STAT‐3) are targets of miR‐20b. The role played by microRNAs (miRNAs) in breast cancer has been mainly studied using tumor cells. In this study, we investigated the expression of miR‐20b in formalin‐fixed paraffin embedded (FFPE) samples, as also as HIF‐1α and STAT‐3, in samples of invasive ductal carcinoma (IDC). The expression of miR‐20b and the proteins HIF‐1α and STAT‐3 was evaluated by real time PCR and immunohistochemistry, respectively. We found that the overexpression of miR‐20b (3‐fold; p&lt;0.05) is accompanied by the downregulation of STAT‐3 (70%; p&lt;0.001) in FFPE samples of IDC. We also observed that HIF‐1α expression in IDC and control samples was not statistically significant. Our results suggest that miR‐20b regulates the expression of HIF‐1α and its transcription factor STAT‐3 in IDC. These findings are relevant since HIF‐1α expression has been correlated with increased intratumoral angiogenesis, cancer progression and poor prognosis in breast cancer.Grant Funding Source: Supported by FAPESP 2012/05235‐3

Novel circulating microRNA signature as a potential non-invasive multi-marker test in ER-positive early-stage breast cancer: A case control study

IntroductionThere are currently no highly sensitive and specific minimally invasive biomarkers for detection of early-stage breast cancer. MicroRNAs (miRNAs) are present in the circulation and may be unique biomarkers for early diagnosis of human cancers. The aim of this study was to investigate the differential expression of miRNAs in the serum of breast cancer patients and healthy controls. MethodsGlobal miRNA analysis was performed on serum from 48 patients with ER-positive early-stage breast cancer obtained at diagnosis (24 lymph node-positive and 24 lymph node-negative) and 24 age-matched healthy controls using LNA-based quantitative real-time PCR (qRT-PCR). A signature of miRNAs was subsequently validated in an independent set of 111 serum samples from 60 patients with early-stage breast cancer and 51 healthy controls and further tested for reproducibility in 3 independent data sets from the GEO Database. ResultsA multivariable signature consisting of 9 miRNAs (miR-15a, miR-18a, miR-107, miR-133a, miR-139-5p, miR-143, miR-145, miR-365, miR-425) was identified that provided considerable discrimination between breast cancer patients and healthy controls. Further, the ability of the 9 miRNA signature to stratify samples from breast cancer patients and healthy controls was confirmed in the validation set (p = 0.012) with a corresponding AUC = 0.665 in the ROC-curve analysis. No association between miRNA expression and tumor grade, tumor size, menopausal- or lymph node status was observed. The signature was also successfully validated in a previously published independent data set of circulating miRNAs in early-stage breast cancer (p = 0.024). ConclusionsWe present herein a 9 miRNA signature capable of discriminating between ER-positive breast cancer and healthy controls. Using a specific algorithm based on the 9 miRNA signature, the risk for future individuals can be predicted. Since microRNAs are highly stable in blood components, this signature might be useful in the development of a blood-based multi-marker test to improve early detection of breast cancer. Such a test could potentially be used as a screening tool to identify individuals who would benefit from further diagnostic assessment.

Micro-RNAs as clinical biomarkers and therapeutic targets in breast cancer: Quo vadis?

Breast cancer (BC) is the most frequent type of non skin cancer among women and a major leading cause of cancer-related deaths in Western countries. It is substantial to discover novel biomarkers with diagnostic, prognostic or predictive usefulness as well as therapeutic value for BC. Micro-RNAs (miRNAs) belong to a novel class of endogenous interfering RNAs that play a crucial role in post transcriptional gene silencing through mRNA targeting and, thus, are involved in many biological processes encompassing apoptosis, cell-cycle control, cell proliferation, DNA repair, immunity, metabolism, stress, aging, etc. MiRNAs exert their action mainly in a tumor suppressive or oncogenic manner. The specific aberrant expression patterns of miRNAs in BC that are detected with the use of high-throughput technologies reflect their key role in cancer initiation, progression, migration, invasion and metastasis. The detection of circulating extracellular miRNAs in plasma of BC patients may provide novel, non-invasive biomarkers in favor of BC diagnosis and prognosis and, at the same time, accumulating evidence has underscored the possible contribution of miRNAs as valuable biomarkers to predict response to chemotherapy or radiotherapy. Data from in vitro and in vivo studies on BC have revealed promising therapeutic approaches via miRNA delivery and miRNA inhibition. The purpose of this review is to explore the ontological role of miRNAs in BC etiopathogenesis as well as to highlight their potential, not only as non-invasive circulating biomarkers with diagnostic and prognostic significance, but also as treatment response predictors and therapeutic targets aiding BC management.

Pathogenic and therapeutic role of miRNAs in breast cancer

MicroRNAs (miRNAs) are small noncoding RNA molecules present in all cell types, with sizes that vary from 18 to 28 nucleotides. miRNAs play significant roles in several biological processes, including development, differentiation, metabolism, initiation, and progression of cancer. In recent years, considerable research has been directed towards identifying miRNAs in peripheral blood from circulating tumor cells and disseminating tumor cells. Because these circulatory miRNAs are very stable and reproducible, their identification could be useful as prognostic markers as well as therapeutic agents for many cancers such as breast cancer. In this article, we review the role of specific circulatory miRNAs in breast cancer, with particular emphasis on their clinical importance.

MiR-205 and miR-200c: Predictive Micro RNAs for Lymph Node Metastasis in Triple Negative Breast Cancer.

PurposeWe examined expression profiles of 16 micro RNAs (miRNAs) in triple negative breast cancers to identify their potential as biomarkers for lymph node metastasis.MethodsThe expression profiles of miR-9, miR-21, miR-30a, miR-30d, miR-31, miR-34a, miR-34c, miR-100, miR-122, miR-125b, miR-146a, miR-146b, miR-155, miR-181a, miR-200c, and miR-205 were examined by using real-time quantitative reverse transcription polymerase chain reaction in tumor samples and corresponding benign breast tissues. Their associations with histopathological features and prognostic parameters were assessed.ResultsWhen compared with the expression in benign breast tissues, seven of the miRNAs (miR-31, miR-205, miR-34a, miR-146a, miR-125b, miR-34c, and miR-181a) were downregulated more than 1.5-fold in tumor tissues, whereas, only miR-21 was found to be upregulated more than 1.5-fold in tumor tissues. Although miR-200c levels were decreased only 1.12-fold in tumor tissues, the reduced expressions of miR-200c and miR-205 were significantly associated with lymph node metastasis (p=0.021 and p=0.016, respectively).ConclusionOur results demonstrate that miR-205 and miR-200c expression levels may be useful in predicting lymph node metastasis in triple negative breast cancer patients.

Abstract P4-07-07: Analysis of miRNAs and proteins relations in breast cancer

Abstract Introduction / Objectives MicroRNAs (miRNAs) constitute a new class of small noncoding RNAs that control post-transcriptionally the expression of gene products, either modulating directly protein translation, or regulating the stability of messenger RNA. There is increasing evidence of the role that miRNAs play in regulating breast cancer gene expression. However, there is little knowledge about the function and targets of miRNAs, and how they regulate complete processes or pathways. The main objective of this study was to unravel biological processes and signaling pathways regulated by miRNAs in breast cancer comparing their expression with the expression of the proteins they regulate. New statistical approaches were conducted in order to associate miRNA and protein quantification results with breast cancer subtype and to evaluate the association of miRNAs and protein expression patterns. Materials and Methods MicroRNA and protein expression were obtained from 79 breast cancer FFPE samples (16 TNBCs and 63 Luminal tumors). RNA was extracted from FFPE samples using RecoverAll (Ambion). MicroRNA expression was analyzed by RT-qPCR using TaqMan Arrays (Applied Biosystems). We selected for subsequent analysis those miRNAs with significant correlation between FF and FFPE samples. Protein extracts from FFPE samples were prepared in 2% SDS buffer using a protocol based on heat-induced antigen retrieval (Gámez-Pozo A et al. Mol Biosyst. 2011; 7: 2368-74). Protein abundance was calculated on the basis of normalized spectral protein intensity (LFQ intensity) using MaxQuant. Probabilistic graphical models are being applied successfully to represent complex biological systems as networks. In this phase of the study, we have chosen an appropriate methodology in the analysis of high dimensional data selecting a forest which minimizes the BIC criterion. This procedure extends the Chow and Liu's approach to the Gaussian case. The software used for implementation is based on the R library gRapHD. Results We measured the expression of 90 miRNAs in 79 breast cancer samples using RT-qPCR. We identified and quantified more than 3000 protein groups. We selected for subsequent analyses more than 1000 quantifiable proteins, defined as those identified at least in 75% of the samples in at least one type of sample with more than two unique peptides. Then, we analyzed the relations between miRNA and protein expressions. We identified miRNAs strongly related with processes considered as hallmarks of cancer, such as cellular adhesion, using probabilistic graphical models. Conclusions The integration of miRNA and protein expression patterns may be useful to describe how miRNAs regulate biological processes and signaling pathways in breast cancer. There is a need of new statistical approaches to evaluate these relations and to obtain meaningful information from such complex and massive data. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-07-07.

MiRNA Dysregulation in Breast Cancer

miRNAs have emerged, in the last decade, as key players in the carcinogenic process, with many candidates identified as playing important roles in many aspects of tumor development, growth, metastasis, and drug resistance. More recently, polymorphisms in miRNAs themselves or in their binding sites in target genes have been identified to incur increased risk of breast cancer in certain populations. In addition, epigenetic regulation and differential expression of processing enzymes has been shown to contribute to the aberrant expression of miRNAs in breast cancer. This review focuses on the area of miRNA dysregulation in breast cancer through both genetic and epigenetic mechanisms, and the impact of this dysregulation on breast cancer risk and resistance to therapies.